Technical Field
The present invention relates to a scanning projector screen.
Related Art
A scanning projector combines laser beams of R, G and B colors subjected to brightness modulation into one beam, and makes them scan on a screen in synchronization with the brightness modulation to form a two-dimensional image on the screen. The scanning projector has a characteristic feature that it is easy to provide high resolution, downsizing and low power consumption compared to a method of projecting two-dimensional images.
As shown as an example in FIG. 4, a scanning projector 400 includes a red laser light source 410R, a green laser light source 410G and a blue laser light source 410B as light sources, and each light source (410R, 410G and 410B) is subjected to an intensity homogenization and collimation as needed and performs and emits laser light. The emitted light from each light source (410R, 410G and 410B) is subjected to brightness modulation in synchronization with the scanning in pixel units.
The respective emitted light pass through collective lenses (412R, 412G and 412B) arranged on optical axes near the light sources (410R, 410G and 410B), thereby providing convergent light. The convergent light of three R, G and B colors are combined into one convergent light within the scanning projector 400.
In the example shown in FIG. 4, the green convergent light is combined (i.e., multiplexed) with the red convergent light by a dichroic mirror 414G, and further the blue convergent light is combined (i.e., multiplexed) with them by a dichroic mirror 414B into one synthetic light. Focal distance and arrangement position of the respective collective lenses (412R, 412G and 412B) are determined such that the respective convergent lights of the respective colors are focused at the same position.
The synthetic light is bent by a mirror 420 for downsizing, and then an irradiation direction of the synthetic light is controlled by a high-speed two-dimensional scanning element 430 and scanned in two-dimension. The high-speed two-dimensional scanning element 430 is an element which performs optical scanning by using a movable mirror 430a. In general, the high-speed two-dimensional scanning element 430 includes a two-dimensional scanning MEMS mirror (MEMS optical scanner); however, vertical scanning and horizontal scanning MEMS mirrors may be combined. Alternatively, a galvanometer mirror may be used.
A rectangular screen 500 of a rectangular shape is arranged on a light-focusing surface of the synthetic light. The screen 500 may be a transmissive type or a reflective type. Synthetic light of each pixel is scanned at a high speed on the screen 500, and therefore two-dimensional image is perceived as a result of an afterimage effect of eyes.
Patent Literature 1: JP 2012-208440 A